1. Field of the Invention
The present invention generally relates to soybean processing and utilization and more specifically to a process for utilizing soy molasses, a by-product in the soy protein concentrate production, for producing purified soy sugars rich in oligosaccharaides.
2. Discussion of the Related Art
Recently there is an increasing interest in oligosaccharaides as food supplements or food additives in health foods. The present invention relates to a process for producing soy sugars of high oligosaccharaide content, from soy molasses, a low cost by-product in the soy protein concentrate production.
Soy is one of the main vegetable sources for both edible oil and high protein foods throughout the world. Whole soybeans contain about 40% protein, 20% fat, 5% ash and 35% carbohydrates on dry matter basis. In the Far East, soy was used as a source for human protein requirement for thousands of years. In the West, by contrast, the majority of soybeans are processed into oil while the high-protein soybean meal is used mainly for various high-protein animal feeds and only to a small extent as a resource for human protein requirement. However, over the last decades, the importance of soy as a source for human protein requirement has been increasingly recognized in the Western market as well, and various human food products based on soy protein are now available for western consumers. Some of these products are based on soy protein concentrates for use as protein sources for human requirement and also as milk powder substitute for calves. The present invention relates to a process for utilizing a by-product of the soy protein concentrate production. Soy concentrates (SPC) is prepared either by aqueous extraction of the whole soybeans or by aqueous ethanol extraction or defatted soybeans flakes. The present invention relates to soy molasses which is obtained as a by-product of the latter process. According tot his method, the starting material for the production of SPC is dehulled, defatted soybean flakes with high protein solubility, known as white flakes. The concentration of protein is increased by removing most of the soluble non-protein constituents by extraction with aqueous ethanol. Soy molasses is the aqueous alcoholic extracts so obtained after the removal of the alcohol and part of the water. The soluble constituents include primarily soluble carbohydrates in the form of mono, di, and oligosaccharides, and also to a much lesser extent proteins of low molecular weight, lipids, and minerals.
Soybean molasses is a low cost material which impose environmental disposal problems and therefore is used mainly as low-cost animal feed ingredient. The main constituents of soy molasses, soy sugars, consist of about 65% mono and di-saccharaide and about 35% oligosaccabraides, mainly, raffinose (5-7%) and stachyose (30-32%). Soy oligosaccharaides are indigestible by humans and monogastric animals and indeed are considered to be the main cause for flatulence and discomfort suffered by soyfood consumption. However, soy oligosaccharaides are useful as growth stimulating agents for bifidobacteria (i.e., are prebiotic agents) which are known to have physiological benefits. Soy oligosaccharaides can also serve as low-sweetness functional additives for food. Recently, with increasing evidence of the potential benefits of “friendly” bifidobacteria, including reducing the risk of colon cancer, soy oligosaccharide are receiving considerable attention as a functional material promoting the growth of bifidobacteria populations. Oligosaccharide are therefore a useful material for relieving constipation, preventing obessity, controlling the aging process and preventing arteriosclerosis. Consequently, the market for soy oligosaccahrides has increased significantly in the last years. Soy oligosaccahrides are also expected to be used in a wide range of foods as a functional material for treating life-style-related diseases.
The present invention provides a method for utilizing soybean molasses, otherwise an environmental burden byproduct and therefore a low-cost animal feed ingredient, in soy processing. According to this method soy molasses are utilized for the production of sugar mixtures of high oligosaccharide content which can be used as food additives to various prebiotic and/or probiotic foods.